Ciliata

The ciliates are single-celled organisms that have cilia, which are tiny hair-like structures that cover part or all of the cell surface. The cilia are driven by tiny molecular motors that are called kinetosomes (natural nanomachines). The cilia move in a coordinated way that propels the organism around in its environment.

Some of the cilia draw food into a mouth-like gullet by which the animal feeds. Bacteria, algae, other small protists, rotting plant stuff serve as food. The ciia create a water current that pushes food into the ciliate cell as little bubbles called food vacuoles. The cell absorbs the food and turns it into energy to power the cell-machine and material for cell growth.

When the cell reproduces by asexual division, the micronuclei divide by mitosis in the usual way, but the macronucleus simply pulls itself apart into two pieces, an imperfect operation that leaves the animals defective after a few hundred generations. Ciliates also reproduce through sexual conjugation, in which the micronuclei split by meiosis and are exchanged. As part of sexual reproduction, the macronucleus is often regenerated by the micronucleus, which fixes the problem of generational weakening of the animals.